1. Field of the Invention
The present invention relates to a method and a system for producing optical tomographic images by OCT (Optical Coherence Tomography) measurement.
2. Description of the Related Art
Conventionally, ultrasonic diagnostic apparatuses (ultrasonographs) have been used to observe lesions in the body cavities of patients. The ultrasonic diagnostic apparatuses obtain and display ultrasonic tomographic images of the lesions as motion images (video images). For example, in Japanese Unexamined Patent Publication No. 2004-344516, the entire area of an image represented by image data is divided into a plurality of areas, and the image data is updated for each of the divided areas to smoothly update the image.
Further, as a method for obtaining tomographic images of tissue in vivo (in living organisms), apparatuses for obtaining optical tomographic images are used, in some cases, in addition to the ultrasonic diagnostic apparatuses. The apparatuses for obtaining optical tomographic images obtain the optical tomographic images by utilizing OCT measurement. For example, Japanese Unexamined Patent Publication No. 2006-280449 proposes an image diagnostic apparatus that obtains an ultrasonic tomographic image and an optical tomographic image at the same time. In Japanese Unexamined Patent Publication No. 2006-280449, the optical tomographic image of only a region of interest (ROI), which is part of the entire image, is obtained, because production of the optical tomographic image requires long image processing time. In Japanese Unexamined Patent Publication No. 2006-280449, the optical tomographic images are obtained as stated above. Therefore, a drop in the frame rate is prevented when the ultrasonic tomographic image and the optical tomographic image are displayed at the same time.
Not only in the configuration disclosed in Japanese Unexamined Patent Publication No. 2006-280449, when the optical tomographic images are displayed as motion images by FD (Fourier Domain)-OCT measurement, it is necessary to obtain tomographic information by performing frequency analysis, such as Fourier transformation. Since the frequency analysis requires predetermined processing time, when a probe is rotationally driven by a user, the update of the tomographic images is delayed from the operation of the probe, in other words, the update of the tomographic images does not synchronize with the operation of the probe. Hence, there is a problem that the motion-image response characteristic of the tomographic images is low.